• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.125.1-125
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• 2001

This paper deals with the eigenvalue assignment technique for linear time-varying systems to achieve feedback stabilization. For this, we introduce the novel eigenvalue concepts. Then, we propose the Ackerman-like formula for linear time-varying systems. It is believed that this technique is the generalized version of the Ackerman formula forlinear time-invariant systems. The advantages of the proposed technique are that it does not require the transformation of the original system into the phase-variable form nor the computation of eigenvalues of the original system.

• The Pure and Applied Mathematics
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• v.15 no.3
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• pp.229-243
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• 2008

This paper is intended to clarify and verify two representation algorithms computing representations of elements of free groups generated by two linear fractional transformations. Moreover in practice some parts of the two algorithms are modified for computational efficiency. In particular the justification of the algorithms has been rigorously done by showing how both algorithms work correctly and efficiently according to inputs with some properties of the two linear fractional transformations.

• Journal of applied mathematics & informatics
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• v.42 no.2
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• pp.237-243
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• 2024

A similarity transformation of a solution of the Cauchy problem for the linear difference equation in Hilbert space has been studied. In this manuscript, we obtain necessary and sufficient conditions for linear equivalence of the discrete semigroup of operators, generated by the solution of the difference equation utilizing four Canonical semigroups.

• Journal of the Korean Society for information Management
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• v.29 no.2
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• pp.193-204
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• 2012

The characteristics of citation and centrality measures in citation networks can be identified using multiple linear regression analyses. In this study, we examine the relationships between bibliometric indices and centrality measures in an article-level co-citation network to determine whether the linear model is the best fitting model and to suggest the necessity of data transformation in the analysis. 703 highly cited articles in Physics published in 2004 were sampled, and four indicators were developed as variables in this study: citation counts, degree centrality, closeness centrality, and betweenness centrality in the co-citation network. As a result, the relationship pattern between citation counts and degree centrality in a co-citation network fits a non-linear rather than linear model. Also, the relationship between degree and closeness centrality measures, or that between degree and betweenness centrality measures, can be better explained by non-linear models than by a linear model. It may be controversial, however, to choose non-linear models as the best-fitting for the relationship between closeness and betweenness centrality measures, as this result implies that data transformation may be a necessary step for inferential statistics.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09b
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• pp.842-845
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• 2005

A method for the numerical simulation of two-dimensional free-surface flow resulting from the propagation of regular gravity waves over topography with arbitrary bottom shape is presented. The method is based on the numerical solution of the Euler equations subject to the fully nonlinear free-surface boundary conditions and the appropriate bottom, inflow and outflow conditions using a hybrid finite-differences and spectral-method scheme. The formulation includes a boundary-fitted transformation, and is suitable for extension to incorporate large-eddy simulation (LES) and large-wave simulation (LWS) terms for turbulence and breaking wave modeling, respectively. Results are presented for the simulation of the free-surface flow over two different bottom topographies, with constant slope values of 1:10 and 1:20, two different inflow wave lengths and two different inflow wave heights. An absorption outflow zone is utilized and the results indicate minimum wave reflection from the outflow boundary. Over the bottom slope, lengths of waves in the linear regime are modified according to linear theory dispersion, while wave heights remain more or less unchanged. For waves in the nonlinear regime, wave lengths are becoming shorter, while the free surface elevation deviates from its initial sinusoidal shape.

• Journal of the Korean Society of Radiology
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• v.11 no.4
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• pp.241-246
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• 2017

The existing fractal compression method is effective in generating an artificial shape by approximating its partial regions to a domain block by re-dividing the whole image into a domain region and dividing it into several domain blocks, but it is difficult to implement a computer. In this study, it is difficult to approximate a complex block such as a large-sized block and an affine transformation because a large amount of calculation is required in searching for a combination of similar blocks through a transformation, so a large amount of coding time is required.

• Communications for Statistical Applications and Methods
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• v.16 no.5
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• pp.781-790
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• 2009

This paper deals with a rank transformation method and a Theil's method based on an ${\alpha}$-level set of a fuzzy number to construct a fuzzy linear regression model. The rank transformation method is a simple procedure where the data are merely replaced with their corresponding ranks, and the Theil's method uses the median of all estimates of the parameter calculated from selected pairs of observations. We also consider two numerical examples to evaluate effectiveness of the fuzzy regression model using the proposed method and of another fuzzy regression model using the least square method.

• Journal of the Korean Society for Heat Treatment
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• v.16 no.2
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• pp.90-96
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• 2003

The effect of betatizing temperature on microstructure and transformation characteristics in a Cu-AI-Ni based pseudoelastic alloy fabricated by heated mold continuous casting by using metallography, XRD and calorimetry. The microstructure of cast rod betatized at $600^{\circ}C$ revealed a ${\beta}_1$ parent phase and a ${\gamma}_2$ phase precipitated along the casting direction. When the cast rod was betatized at the elevated temperature above $600^{\circ}C$, the ${\gamma}_2$ phase is completely dissolved into the matrix so that the volume fraction of the ${\gamma}_2$ phase was decreased. The parent phase was stabilized by betatizing at $600^{\circ}C$. However, the ${\beta}_1$ parent phase was transformed to both ${{\beta}_1}^{\prime}$ and ${{\gamma}_1}^{\prime}$ martensites with increasing betatizing temperatures above $600^{\circ}C$, while $M_s$ and $A_s$ temperatures were decreased. The stress-strain curves for compression test were not same with betatizing temperature; the stress-strain curves of the specimen betatized at $600^{\circ}C$ and $700^{\circ}C$ were linear but those of the specimen betatized at $800^{\circ}C$ and $900^{\circ}C$ were not linear.

• Wind and Structures
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• v.3 no.4
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• pp.221-241
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• 2000

Structural dynamics usually applies modal transformation rules aimed at de-coupling and/or minimizing the equations of motion. Proper orthogonal decomposition provides mathematical and conceptual tools to define suitable transformed spaces where a multi-variate and/or multi-dimensional random process is represented as a linear combination of one-variate and one-dimensional uncorrelated processes. Double modal transformation is the joint application of modal analysis and proper orthogonal decomposition applied to the loading process. By adopting this method the structural response is expressed as a double series expansion in which structural and loading mode contributions are superimposed. The simultaneous use of the structural modal truncation, the loading modal truncation and the cross-modal orthogonality property leads to efficient solutions that take into account only a few structural and loading modes. In addition the physical mechanisms of the dynamic response are clarified and interpreted.

• 한국전산유체공학회:학술대회논문집
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• 2000.05a
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• pp.99-106
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• 2000

A method of two and three dimensional orthogonal grid generation with control of spacing by using the covariant Laplace equation is Presented. An important feature of the methodology is its ability to control effectively the grid spacing especially near the boundaries still maintaining good orthogonality in whole field. The method is based on the concept of decomposition of the global transformation into consecutive transformation of an approximate conformal mapping and au auxiliary orthogonal mapping to have linear and uncoupled equations. Control of cell spacing is based on the concept of reference arc length, and orthogonal correction is performed in the auxiliary domain. It is concluded that the methodology can successfully generate well controlled orthogonal grids around bodies of 2 and 3 dimensional configurations.